Not applicable.
Not applicable.
The present invention relates generally to electronic pest deterrent devices and more particularly to pest deterrent devices that emit ultrasound to drive off animals.
Pests, such as birds, deer, cats, dogs, or rodents among others, can cause significant damage to crops, buildings, stored goods, and landscaping. A variety of methods and devices have been employed to attempt and reduce the damage caused by pests. Some approaches use a scarecrow or replica of a predator, such as an owl or snake, to scare away pests. Unfortunately, pests often become accustom to these devices and they lose their effectiveness.
Other approaches use noise, such as a series of small explosive devices linked to a slow-burning fuse, and/or propane guns to scare away pests. Such methods might be inappropriate in an area where the noise would be bothersome. Additionally, the pests or pest might become accustomed to the repeating noise.
Yet other methods use a detector, such as a motion sensor, to detect the presence of a pest and trigger a pest deterrent event, such as a noise. Many such detectors work automatically, emitting a loud sound or tone when movement is detected. Some pest deterrent devices avoid disrupting human activity or comfort by generating just ultrasound, which is beyond the range of human hearing. However, some pests may still become accustomed to the regular sound, even a fairly loud regular sound. Another issue is that ultrasonic pest deterrent devices can consume a fairly large amount of power to produce high levels of ultrasound. Power consumption is not much of an issue if a power outlet is available, but becomes more of an issue if the deterrent device is operating on battery power. Finally, a user might not be able to tell if the unit is working, i.e. emitting sound, because the sound is above his range of hearing.
Problems associated with power drain can be compounded if the detector keeps triggering off of continuous motion of the pest. Similarly, many detectors, such as passive infrared (xe2x80x9cPIRxe2x80x9d) or Doppler detectors provide low outputs that must be amplified to turn on relatively high-power devices like ultrasound generators. Draw on the power supply and ground current feedback can affect the operation of the detector-amplifier circuit, causing unreliable triggering.
Accordingly, it is desirable to provide an automatic pest deterrent method and apparatus that more effectively drives off pests. It is further desirable that the apparatus be efficient to allow operation in remote locations using battery power. It is yet further desirable that the user be able to verify that the unit is providing sound.
An efficient pest deterrent device uses a detector that provides a detection signal to a microprocessor. The microprocessor is used to directly generate ultrasound, as well as control the operation and timing of the device. For example, the microprocessor can detect if the device is operated on line or battery power, and change device operation to conserve power when the device is battery-operated. The device can thus operate in a variety of modes. On line power, the device alternates between two ultrasonic tones until a pest is detected, at which point the devices changes the ultrasonic output to a sweeping output. The ultrasonic sweep can be combined with a flash, preferably delayed from the onset of the swept signal by about one second. This delay allows the attention of the pest to be drawn to the ultrasound, and the flash to startle or otherwise drive off the pest. That is, the delay time period is sufficient for the pest to look at the ultrasonic output. In a further embodiment, the strobe charging circuit""s oscillator signal can be used to amplitude modulate (xe2x80x9cAMxe2x80x9d) the ultrasound to create noisy sidebands from high ultrasonic down to within the normal range of human hearing. This AM creates even more disturbing ultrasound and also allows an operator to conveniently verify sonic output but at much lower sound levels than the ultrasound.
In one embodiment, a microprocessor-controlled pest deterrent device has a passive infrared sensor that produces a train of alternating positive and negative pulses that are buffered and amplified. The microprocessor is programmed to initiate pest deterrent signals, i.e. activate a load, when an input voltage signal of a selected polarity rises above a threshold level. The load is not active when the input is below the threshold or of the opposite polarity. The input signal is provided to the microprocessor by an amplifier and is fed back through a coupling capacitor as positive feedback to the input of the operational amplifier, which saturates the operational amplifier. After a selected period of time, the capacitor charges and causes an inverse input signal fed back to the input through the same coupling capacitor, which turns off the load after a selected period of time.
The operational amplifier then saturates to the opposite rail. Again, the output is coupled through the coupling capacitor as positive feedback causing the capacitor to discharge. During this selected discharge period, the load is off and the activation circuitry will not trigger off of a pulse from the sensor or other signal, in other words, the sensor is locked out because the input to the microprocessor is of the wrong polarity for activating the load.
In a particular embodiment, the pest deterrent device includes both a strobe light and ultrasonic speakers. When a pest is detected, the device either initiates ultrasound or changes the ultrasonic output. After a selected period of time, which can be programmed in the microprocessor, the strobe is activated and flashes several times for a brief period and then remains off. In one timing sequence, sweeping ultrasound is activated when a pest is detected and one second later the strobe flashes about five times in one half second. The sweeping ultrasound remains on for an additional one and one-half seconds, thus the deterrent event lasts a total of three seconds. The load is then locked out for a period of time to avoid continuous triggering or even self-triggering, such as by the strobe being detected or electronic noise emulating a triggering event.
In yet another embodiment, a high level of ultrasonic energy is produced by using four ceramic speakers in a series-parallel configuration. Each speaker has a nominal input capacitance of about 0.2 micro-Farads, and the four-speaker series-parallel also has a nominal input capacitance of about 0.2 micro-Farads. This is approximately twice the capacitance of conventional ultrasonic speakers, and achieves a higher peak-to-peak resonant voltage on 12 V battery power or 18 V line power, and over 120 dB of ultrasonic power.